Arif R.
Karim
,
Anthony
Linden
,
Kim K.
Baldridge
* and
Jay S.
Siegel
*
Organisch-chemisches Institüt, Universität Zürich, Winterthurerstrasse 190, Zürich, CH-8057, Switzerland. E-mail: kimb@oci.uzh.ch; jss@oci.uzh.ch
First published on 24th May 2010
The central ring of a 1,4-bis(arylethynyl)arene (ditolan) can be viewed as a molecular rotor with an extremely low barrier to rotation in the gas phase or solution. The torsional energy profile of that ring is shown to be dependent on the relative conformation of the end capping arenes. When the capping arenes are sterically bulky m-terphenyl units, it is possible to rationalize the conformational dynamics of the central ring by a factorization analysis, involving perturbation of the basic torsional energy profile by polar-π, and dispersion interactions between the flanking rings of the cap and the central ring of the ditolan. The symmetry of the construct can modulate the effect of these interactions. These principles apply to the design of materials in which a steric shroud excludes packing distortions.
A well-known principle of conformational analysis is that, for otherwise equal systems, an increase in the symmetry of the conformational profile results in a decrease in the barrier to rotation.35 This idea may be viewed as a stereochemical corollary to the Hammond postulate in so far as conformations that are close in structure tend to be close in energy, and arriving back at the same conformation in fewer radians implies a closer structural, hence closer energetic, relation of the intermediate conformations.36
In tolan, there are two principal arenes (A and B), one at each end of the alkyne, with a slight preference to align coplanar with one another across the alkyne.12 The structure of 2,6-diaryltolans displays an umbrella-like conformation in which the alkyne is nestled between the two flanking arenes situated in the ortho positions of ring A (Fig. 1). In the idealized CPK model geometry of conformation α, the ortho-hydrogen atoms of ring B sit just outside vdW contact with the face of the flanking rings. Thus, no direct steric repulsion ensues; however, the possibility of CH-π/polar-π as well as attractive dispersive interactions still exists. A 90° rotation of ring B (conformation β) eliminates the CH-π interaction and places ring B orthogonal to ring A.
Fig. 1 Principal conformations (α and β) of a 2,6-diaryltolan. |
Extending the structure to a ditolan (1,4-bis(arylethynyl)arene) makes for three principal rings (A, B, and A′) and creates four fundamental high symmetry conformations: two in which rings A and A′ are coplanar (||α/||β) and two in which they are orthogonal to one another (⊥α/⊥γ). Conformations ||α and ||β interconvert by 90° rotation of ring B; and conformations ⊥α and ⊥γ interconvert by 45° rotation of ring B (Fig. 2).
Fig. 2 Principal conformations of a generic tetraarylditolan: (top) rings A and A′ are coplanar (||) and ring B is either coplanar (α) or orthogonal (β); (bottom) rings A and A′ are orthogonal (⊥) and ring B is either coplanar to one ring A or A′ (α), or skewed to both (γ). |
In type ||, the 90° rotation of ring B interconverts diastereomeric conformations, each of D2h symmetry, which represent the maximum and minimum of a 2-fold conformational profile. In ⊥, the 90° rotation of ring B interconverts homomeric conformations of D2d symmetry, which represent equipotential conformations on a 4-fold conformational profile; a skewed structure with equal torsion angles of 45° between ring B and either ring A or A′ is the transition structure. Thus, control of the relative conformation of the end terphenyls (acting as stators) changes the symmetry of the conformational profile of the central ring (acting as rotator).
The hypothesis is that conformations of type || will display higher than “normal” barriers to rotation in 2,2′,6,6′-tetraarylditolans, and those of type ⊥ will lead to barriers lower than “normal.” Furthermore, conformations of type ⊥ could set up a steric shield around ring B, which could allow similar rotational dynamics in the crystal as in solution. The caveat here is always the uncertainty as to what extent crystal packing forces will cause structural perturbation.37
The magnitude of the difference between rotational barriers of types || and ⊥ will depend to a large extent on the nature and strength of the CH-π interaction in these systems.38,39 Thus, umbrella-like 2,6-diaryltolans provide a useful model system for experimental and computational assessment of these interactions. Data on the umbrella-like systems provide a basis for creating an empirical factorization of effects on the barrier to rotation, the additivity of which can be tested in the 2,2′,6,6′-tetraarylditolans of family 2.
Several model systems have been studied to parse out aspects of the aryl-aryl interaction.41–43 Specific studies into the so-called polar-π effect have led to a model for aryl-aryl interactions that includes dispersion, static polarity, and induced dipolar effects.44–47 Such a model is further supported by extensive theoretical work predicting the repulsive nature of the PS disposition and the attractive nature of both the PO and EF dispositions.48 This model provides a simple empirical way to rationalize the nature of a variety of arene-arene interactions.49–53
Until recently, quantum-mechanical methods that account for dispersive interactions well were too resource intensive to implement for systems of 30–60 non-hydrogen atoms. Commonly used DFT methods like B3LYP neglect dispersive interactions.54,55 More modern DFT functionals attempt to include effects due to dispersive terms.56,57 The combination of results from both DFT method types provides an impression of the relative importance of dispersive interactions in a specific system.
In the present study, the EF and PO arrangements most closely model the α and β conformations of ring B, respectively. Given the energy difference between α and β conformations in the parent tolan, one can assume that the change in ΔE(β − α) is a measure of the ΔE(PO − EF) in this system. This assumption is not an absolute but a useful working model for deducing semi-quantitatively the factors that contribute to such arene-arene interactions. The EF interaction has also been considered as a CH-π interaction.58
Fig. 4 Families 1 (umbrella tolans), 2 (ditolans), and 3 (ditolylcyclophanes/catenanes). |
The synthesis of family 1 derivatives starts with an alkynyl coupling to 2,6-dibromoiodobenzene and passes through intermediates 6a–d (Scheme 1).59 Subsequent Negishi coupling with mesitylzinc chloride yields 1a–d:60,61 Ar = phenyl (1a), 2-pyridyl (1b), 3-pyridyl (1c), and 2-pyrimidyl (1d).
Scheme 1 i. ArCCH, Pd(PPh3)2Cl2, CuI, TEA; ii. TMSCCH, Pd(PPh3)4, CuI, TEA; iii. K2CO3, MeOH; iv. 2-iodopyrimidine, Pd(PPh3)4, TEA; v. MesitylZnCl, Pd(PPh3)4, THF. |
Members of family 2 were prepared from 5-TMS by Pd mediated coupling with m-anisyl zincate to make intermediate 7-TMS/Me (Scheme 2). Desilylation of 7-TMS/Me with carbonate and subsequent coupling with diiodobenzene, 2-bromo-5-iodopyridine or diiodobiphenyl resulted in 2a-Me, 2b-Me or 2c-Me, respectively. The synthesis of the desmethyl version of 2a-Me (2a-H) began with protection of 4-bromo-3,5-dimethylphenol with tert-butyldimethylsilylchloride, from which the arylzinc halide was prepared and used to couple with 5-TMS under Pd mediated Negishi conditions.60,61 The resulting m-terphenylacetylene (7-TMS/TBDMS) was deprotected and then set to couple with 1,4-diiodobenzene under Pd mediated Sonogashira conditions to produce 2a-H.59
Scheme 2 i. 2,6-diMe-4MeOPhZnCl, Pd(PPh3)4, THF; iii. K2CO3, MeOH; (ii. 2,6-diMe-4TBDMSOPhZnCl, Pd(PPh3)4, THF; iv. K2CO3, MeOH); v. 1,4-diiodobenzene, Pd(PPh3)2Cl2, CuI, TEA; vi. 2-bromo-5-iodopyridine, Pd(PPh3)4, TEA; vii. 4,4′-diiodobiphenyl, Pd(PPh3)4, CuI, TEA. |
A cyclophane of family 3 was prepared by alkylation of 2a-H with propargyl bromide to provide 2a-CH2CCH, the precursor to cyclophane 3 (Scheme 3), which was obtained by intramolecular oxidative alkyne–alkyne coupling mediated by copper(II).62 As a set, 2a, 2b, and 3 are all targets to mimic type || systems.
A catenane of family 3 has not yet been completed, but an analog of the desired twisted type III conformation was prepared by extending the flanking 2,2′,6,6′ arenes as rigid biphenyls (2d) (Scheme 4). The zinc halide reagent of 4-(4-bromo-3,5-dimethylphenyl)anisole was used to couple with 5-TMS under Pd mediated Negishi conditions. The resulting m-terphenylacetylene (8) was deprotected and then set to couple with 1,4-diiodobenzene under Pd mediated Sonogashira conditions to produce 2d, a potential precursor to a concatenated ditolan.
Scheme 4 i. Pd(PPh3)4, THF; ii. K2CO3, MeOH; iii. 1,4-diiodobenzene, Pd(PPh3)4, CuI, TEA. |
A side reaction of the Sonogashira reaction of 7-H/Me led to the diyne dimer (9), presumably through a Pd mediated version of an alkyne-coupling reaction (Scheme 5). Though not directly cogent to our discussion of tolan based rotors, its structure depicts well how steric effects alone might achieve the same goals as the catenane.
Scheme 5 i. Cu(OAc)2·H2O, EtOH. |
Initial computational studies focused on three symmetrical derivatives of family 1 with flanking mesityl rings on ring A, and phenyl (1a), 2,6-difluorophenyl (1aF), or 2-pyrimidyl (1d) as ring B, all compared against either a reference (parent) compound without flanking rings (1a′, 1a′F and 1d′), or a cognate with pentafluorophenyls instead of mesityl (1a′′, 1a′′F and 1d′′). From this series, the parent conformational preference, ΔE(ref), in the absence of flanking arenes can be established from the difference in energy of the β and α conformations of the reference compound (1a′, 1a′F or 1d′). The difference in energy of the β and α conformations of the aryl substituted compounds, ΔE(β − α), for (1a′, 1a′F and 1d′) or (1a′′, 1a′′F and 1d′′) are assumed to comprise a component arising from the parent ΔE(ref) and a component attributable to the interaction between the edge of ring B and the face of ring A, ΔE(edge/face).
On the basis of previous studies,34–37 mesityl (M) and pentafluorophenyl (P) should have opposite electrostatic effects, with mesityl showing larger interaction energies, (E(estat)). In contrast, polarizability and dispersion (E(disp)) effects of the arene π face should operate in both cases to a similar end. From the perspective of the edge side of the interaction, CH should be δ+, whereas CF and N: should be δ−. The magnitude of the dispersive interactions of these three groups should follow the order, N: < CH < CF.
This admittedly simple analysis provokes an empirical formula of the following form:
ΔE(β − α) = ΔE(ref) + E(edge/face) |
E(edge/face) = E(estat)X/Y + E(disp)X/Y |
X = N:, CH, or CF and Y = M or P |
N:/M < CF/M < CH/P < 0.0 kcal mol−1 < N:/P < CF/P < CH/M |
N:/M = N:/P < CH/M = CH/P < CF/M = CF/P |
Using the data in Table 1, along with the acknowledgement that B3LYP does not account for dispersion effects,63 whereas B97-D does,64 one comes to a presumptive set of basic quantitative values for the interaction terms: (1) the E(estat)X/Y series follows as N:/M (−1.2) < CF/M (−0.7) < CH/P (−0.3) < 0.0 kcal mol−1 < N:/P (0.4) < CF/P (0.9) = CH/M (0.9); and (2) the E(disp)X/Y series follows as N:/M = N:/P (0.3) < CH/M = CH/P (0.6) < CF/M = CF/P (1.0) kcal mol−1. Adding the two terms together, one arrives at E(edge/face) terms of N:/M (−0.9) < CF/M (0.3) < CH/P (0.3) < N:/P (0.7) < CH/M (1.5) < CF/P (1.9) kcal mol−1. ΔE(ref) is between 1.1 and 1.3 kcal mol−1.
Modela | 1a | 1a′ | 1a′′ | 1d | 1d′ | 1d′′ | 1aF | 1a′F | 1a′′F |
---|---|---|---|---|---|---|---|---|---|
a A: B3LYP/DZV(2d,p); B: B97-D/DZV(2d,p); C: MP2/DZV(2d,p); D: M06/DZV(2d,p); E: Empirically fit. | |||||||||
A | 1.86 | 0.98 | 0.65 | 0.20 | 1.43 | 1.65 | 0.58 | 1.26 | 2.15 |
B | 2.47 | 1.11 | 1.39 | 0.50 | 1.53 | 1.96 | 1.62 | 1.40 | 3.29 |
C | 3.09 | 0.65 | — | 0.21 | 0.94 | — | 1.26 | 0.98 | — |
D | 2.59 | 0.87 | 1.37 | 0.41 | 1.31 | 1.87 | 1.66 | 1.18 | 3.03 |
E | 2.6 | 1.1 | 1.4 | 0.4 | 1.3 | 2.0 | 1.6 | 1.3 | 3.2 |
These values not only account for the set of 9 basis compounds, but they also predict the conformational energies in family 2 quite well. Although, no general transferability of these values is warranted, this analysis supports the hypothesis that these effects are energetically small and additive within the scope of this model. It shows that standard intuition concerning the reduction of these interactions into qualitative physical organic components results in a simplifying abstract model. It further highlights the importance of dispersive effects, especially in the context of F for H replacement.47
X-Ray diffraction quality crystals of 1a–1d were grown, diffraction data sets collected, and structures solved/refined.† No derivative of family 1 adopts an idealized α or β conformation in the crystal. The dihedral angles between the planes of the A and B arenes are intermediate between conformations α and β, and the alkyne axis is bent substantially away from linearity (Table 2, Fig. 5, Fig. 6). Computations starting from the crystal structure geometry of 1a predict a very small distortion energy, optimizing back to the idealized 1a in the α conformation as the minimum energy structure. Therefore, one can assume that the potential energy surface is very soft about the ideal α conformation and the distortions in the crystal structure are due to packing forces.
Fig. 5 Geometrical parameters considered in Table 2. |
Compound | A//Ba | θ 1 | θ 2 | θ exo | θ endo | d plane | d atom |
---|---|---|---|---|---|---|---|
a A//B = dihedral angle between rings A and B. b 1a_α is the computational geometry for 1a in the α conformation. | |||||||
1a | 34.32(11) | 118.39(16) | 119.48(16) | 173.2(2) | 173.1(2) | 2.89 | 2.95 |
1a_αb | 0.0 | 121.17 | — | 180.0 | 180.0 | 3.89 | 4.10 |
1b | 33.97(7) | 118.28(10) | 119.26(10) | 171.03(13) | 174.12(12) | 2.90 | 2.95 |
1c | 23.30(11) | 120.54(17) | 120.19(17) | 177.7(2) | 176.9(2) | 3.71 | 3.89 |
41.75(11) | 119.59(18) | 121.38(18) | 177.0(2) | 177.6(2) | 3.60 | 3.79 | |
1d | 47.5(6) | 119.05(15) | 119.05(15) | 177.2(15) | 180.0 |
Fig. 6 X-Ray diffraction structures of 1a–1d. |
In the series 1a–1d, the ortho positions of ring B are two CH bonds, one CH bond, and one N: lone pair, or two N: lone pairs. In all cases where a CH bond is present, the B ring twists to place the CH vector roughly over the position ortho to the methyl groups of the mesitylene, and the alkyne axis bends in favor of a closer CH to arene interaction. Where no CH bond is presented, the arene A-to-B dihedral angle is large and approximates a conformation of the β type. This mode of alkyne bending in the X-ray crystal structure presents itself also in compounds of family 2, albeit placing the CH vector over the methyl bearing carbon (see below). Although no such distortion is predicted by the computations, the energy needed to distort into this conformation is predicted to be very low. It is likely that these crystal structures represent a low energy mode of distortion caused by packing forces.
Method | 2-|| | 2-⊥ | 2′-|| | 2′-⊥ | 2F-|| |
---|---|---|---|---|---|
B3LYP | 3.96 | −0.05 | 2.19 | −0.23 | 1.51 |
B97-D | 5.31 | −0.16 | 2.53 | −0.30 | 3.76 |
MP2 | — | — | 1.48 | −0.09 | — |
M06 | 5.38 | −0.42 | 1.98 | −0.22 | 3.67 |
Empirical | 5.2 | 2.2 | 3.2 |
Synthetic derivatives (2a, 2b and 2c) of family 2 provided solvated crystals suitable for X-ray crystallographic analysis (Fig. 7). In 2c, there are two geometrically similar molecules in the asymmetric unit. They all adopt a type ||α structure and show a serpentine distortion of the ditolan axis, again favoring proximity between an ortho CH bond and the face of a flanking arene. The molecules of 2a and 2b sit across crystallographic centres of inversion. As a consequence, the N: atom and related para CH group in 2b are disordered over two sites, both of which lie to the wayward side of the ditolan-to-arene interaction. The consistent structural distortion across families 1 and 2 and the consistent placement of CH proximal and N: distal to the flanking arene further speaks of a stabilizing CH-to-arene interaction. In all cases, the closest CH bond to arene-ring-atom contact is at the carbon ortho to the methoxy substituent (3.00 Å [2a], 3.05 Å [2b] and 3.29 Å as the avg. of 3.10, 3.26, 3.34 and 3.45 Å [2c]). The central biaryls of 2c adopt a torsion angle close to 15°, suggesting no torsional inhibition of conjugation from end to end of the conjugated π system.
Fig. 7 X-Ray diffraction structures of 2a, 2b and 2c (molecule A). |
The fourth synthetic derivative (2d) of family 2 bears extended diaryl arms in the 2,2′,6,6′ positions (Fig. 8). These were designed to create steric repulsion between substituents on ring A and ring A′, and thereby distort the conformation away from type || toward type ⊥. Crystals of 2d suitable for X-ray crystallographic analysis were grown and the structure solved. The conformation of 2d twists away from type || as predicted; however the dihedral angle between rings A and A′ (42.37(9)°) is intermediate between type || and ⊥. The relationship between rings A and B presents a relatively small dihedral angle of ca. 10°, whereas the dihedral angle between rings B and A′ is close to 33°. The angle distortion of the alkynes is now very small, with an average close to 178°. The distances between the hydrogen atoms on ring B and the carbon atoms of the flanking arenes are also much larger, the closest being 3.39 Å from a carbon meta to the aryl substituent. Most of the contacts exceed 3.6 Å, thus well outside the vdW radii of H and a carbon π system. These structural parameters support the idea that conformations of type ⊥ will display no preferential interactions and therefore manifest effectively high symmetry conformational profiles and lower barriers to rotation.
Fig. 8 X-Ray diffraction structure of 2d. |
The full potential of this steric exclusion design has not been achieved but there is still promise in this approach. The side product 9, although not in the tolan series, gives some insight into what would happen if the steric interactions among the flanking rings could be increased.65 The crystal structure of 9 (Fig. 9) shows a dihedral angle between the terminal aryl rings of over 50°. Extremely bulky and rigid units such as tetraarylmethanes or centaryltricornans could induce such structures to adopt conformations even closer to the type ⊥ ideal.
Fig. 9 X-Ray diffraction structure of 9. |
Fig. 10 X-Ray diffraction structure of macrocycle 3. |
Compound | A//Ba | θ exo | θ endo | d atom |
---|---|---|---|---|
a A//B = dihedral angle between rings A and B. b Two molecules in the asymmetric unit. c Dihedral angles are not representative, torsion angles are about 3, 8, 12, and 22°, see X-ray data. | ||||
2a | 7.57(11) | 174.6(2) | 174.1(2) | 3.00 |
2b | 6.70(14) | 174.5(2) | 174.0(2) | 3.05 |
2c | —c | 174.6(4) | 173.1(4) | 3.10 |
175.3(4) | 171.8(4) | 3.26 | ||
176.8(4) | 174.1(4) | 3.34 | ||
175.4(4) | 177.0(4) | 3.45 | ||
2d | 10.06(9) | 178.1(2) | 176.5(2) | 3.39 m |
[A//B] | [A] | [A] | 3.63 o | |
33.57(9) | 177.6(2) | 178.3(2) | ||
[B//A′] | [A′] | [B] | ||
42.37(9) | ||||
[A//A′] | ||||
3 | 6.4(2) | 174.7(5) | 169.9(5) | 2.86 |
3.3(2) | 173.6(5) | 169.4(5) | 2.90 |
a Weighting scheme: w−1 = σ2(Fo2) + (aP)2 + bP where P = (Fo2 + 2Fc2)/3. b Non-merohedrally twinned by a 2-fold rotation about b*, with a major twin fraction of 0.68. | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Compound | 1a | 1b | 1c | 1d | 2a | 2b | 2c | 2d | 9 | 3 |
Crystallised from | CH2Cl2 | CH2Cl2–EtOH | CH2Cl2–MeOH | CH2Cl2–EtOH | CH2Cl2–hexane | CH2Cl2–EtOH | CH2Cl2–EtOH | CH2Cl2–EtOH | CH2Cl2–EtOH | CH2Cl2 |
Empirical formula | C32H30 | C31H29N | C31H29N | C30H28N2 | C66H72Cl4O4 | C61H61Cl8NO4 | C64H58O4 | C82H70O4 | C52H50O4 | C66H50O4 |
Formula weight/g mol−1 | 414.59 | 415.58 | 415.58 | 416.56 | 1071.10 | 1155.78 | 891.16 | 1119.45 | 738.96 | 907.12 |
Crystal colour, habit | Yellow, prism | Colourless, prism | Colourless, prism | Pale-yellow, plate | Colourless, tablet | Colourless, prism | Colourless, tablet | Colourless, prism | Colourless, plate | Colourless, prism |
Crystal dimensions/mm | 0.12 × 0.27 × 0.30 | 0.20 × 0.20 × 0.25 | 0.12 × 0.25 × 0.27 | 0.05 × 0.20 × 0.25 | 0.10 × 0.17 × 0.40 | 0.15 × 0.20 × 0.25 | 0.10 × 0.25 × 0.30 | 0.20 × 0.20 × 0.30 | 0.03 × 0.17 × 0.28 | 0.13 × 0.18 × 0.23 |
T/K | 160 (1) | 160(1) | 160 (1) | 160(1) | 160(1) | 160(1) | 160(1) | 1601) | 160(1) | 160(1) |
Crystal system | Triclinic | Triclinic | Triclinic | Orthorhombic | Triclinic | Triclinic | Monoclinic | Monoclinic | Monoclinic | Monoclinic |
Space group | P | P | P | Pnna | P | P | P21/c | P21/c | Pc | Cc |
Z | 2 | 2 | 4 | 4 | 1 | 1 | 8 | 4 | 4 | 4 |
Reflections for cell determination | 4275 | 6886 | 8433 | 2427 | 5006 | 52011 | 18356 | 13211 | 7705 | 4677 |
2θ range for cell determination/° | 4–50 | 4–60 | 4–50 | 4–50 | 4–50 | 4–50 | 4–50 | 4–52 | 4–50 | 4–50 |
Unit cell parameters | ||||||||||
a/Å | 8.4200(4) | 8.3091(2) | 10.1034(4) | 18.9732(7) | 9.5378(3) | 9.5501(2) | 21.7475(7) | 29.4698(4) | 12.9195(3) | 35.618(1) |
b/Å | 10.4450(4) | 10.5240(2) | 14.8715(6) | 14.5707(5) | 11.7657(4) | 11.9607(3) | 36.719(1) | 13.9924(2) | 26.1804(7) | 9.3960(3) |
c/Å | 15.4972(7) | 15.4592(3) | 17.8686(7) | 8.6223(4) | 13.6855(6) | 13.4618(3) | 12.9048(4) | 16.0684(2) | 13.8321(3) | 14.9250(4) |
α/° | 81.045(3) | 80.8186(9) | 74.014(3) | 90 | 85.769(2) | 85.759(2) | 90 | 90 | 90 | 90 |
β/° | 74.819(3) | 74.994(1) | 75.146(2) | 90 | 88.725(2) | 88.837(1) | 95.539(1) | 102.4965(8) | 114.575(1) | 92.473(2) |
γ/° | 68.224(3) | 67.878(1) | 78.920(2) | 90 | 71.627(2) | 71.180(1) | 90 | 90 | 90 | 90 |
V/Å3 | 1218.90(10) | 1206.70(4) | 2473.3(2) | 2383.7(3) | 1453.51(9) | 1451.48(6) | 10257.0(6) | 6468.9(2) | 4254.7(2) | 4990.2(3) |
F(000) | 444 | 444 | 888 | 888 | 568 | 602 | 3792 | 2376 | 1576 | 1912 |
D x /g cm−3 | 1.130 | 1.144 | 1.116 | 1.161 | 1.224 | 1.322 | 1.154 | 1.149 | 1.154 | 1.207 |
μ(Mo-Kα)/mm−1 | 0.0634 | 0.0653 | 0.0637 | 0.0674 | 0.251 | 0.434 | 0.0703 | 0.0690 | 0.0713 | 0.0737 |
Scan type | ω | ϕ and ω | ω | ω | ω | ω | ω | ϕ and ω | ϕ and ω | ω |
2θ(max)/° | 50 | 60 | 50 | 50 | 50 | 50 | 50 | 52 | 50 | 50 |
Transmission factors (min; max) | — | — | — | — | — | 0.889; 0.967 | — | — | — | — |
Total reflections measured | 17941 | 30830 | 32418 | 28593 | 19536 | 19022 | 101722 | 99005 | 65817 | 36176 |
Symmetry independent reflections | 4301 | 7037 | 8627 | 2112 | 5099 | 5070 | 18117 | 95938 | 7536 | 4402 |
R int | 0.059 | 0.046 | 0.055 | 0.089 | 0.069 | 0.067 | 0.100 | 0.088 | 0.084 | 0.090 |
Reflections with I > 2σ(I) | 3093 | 4918 | 6228 | 1506 | 2948 | 3558 | 9010 | 67864 | 5363 | 3928 |
Reflections used in refinement | 4298 | 7032 | 8625 | 2109 | 5094 | 5069 | 18108 | 95938 | 7532 | 4402 |
Parameters refined | 296 | 296 | 590 | 178; 36 | 287 | 287 | 1250 | 789 | 1034; 2 | 639; 2 |
Final R(F) [I > 2σ(I) reflections] | 0.0530 | 0.0558 | 0.0546 | 0.0485 | 0.0661 | 0.0786 | 0.0876 | 0.0868 | 0.0526 | 0.0724 |
wR(F2) (all data) | 0.1430 | 0.1591 | 0.1458 | 0.1312 | 0.1903 | 0.2454 | 0.2100 | 0.2708 | 0.1166 | 0.1890 |
Weighting parameters a; ba | 0.0552; 0.3424 | 0.0734; 0.1784 | 0.0574; 0.7937 | 0.0612; 0.3266 | 0.1087; 0 | 0.1749; 0 | 0.0359; 7.7552 | 0.1085; 11.9 | 0.0555; 0.0332 | 0.1465; 0.7217 |
Goodness of fit | 1.067 | 1.054 | 1.055 | 1.060 | 0.965 | 1.018 | 1.104 | 1.153 | 1.091 | 1.073 |
Secondary extinction coefficient | 0.033(5) | 0.027(7) | 0.017(2) | 0.008(2) | 0.030(5) | 0.06(1) | 0.0008(2) | 0.0110(3) | 0.0215(9) | — |
Final Δmax/σ | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.05 | 0.001 |
Δρ (max; min)/e Å−3 | 0.23; −0.18 | 0.27; −0.27 | 0.19; −0.16 | 0.22; −0.19 | 0.26; −0.21 | 0.27; −0.29 | 0.41; −0.20 | 0.67; −0.64 | 0.19; −0.19 | 0.40; −0.28 |
Footnote |
† Electronic supplementary information (ESI) available: Computational methods and coordinate files, experimental procedures and analytical data for compounds prepared in this work. CCDC reference numbers 763789–763798. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0sc00117a |
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